986,269. Shock absorbers. BENDIX CORPORATION, W. T. HARKEY, and L. S. CRANE. April 6, 1961 [May 10, 1960], No. 12421/61. Heading F2S. [Also in Division B7] A railway flat car 20, Fig. 1, has a platform 22, for cargo 24, movable relative to the vehicle frame 26 during excessive acceleration or deceleration, resilient means operative to urge the platform to a centred position on the frame and hydraulic shock absorbing means 25 connected between the frame and platform to dissipate the kinetic energy of the moving platform by flow of liquid forced through a variable area metering orifice to resist displacement of the platform relatively to the frame with a force which increases at a variable rate as the amount of movement of the platform away from its centred position increases. As shown in Figs. 2 and 3, the platform is comprised of longitudinal beams 42 and transverse beams 44, the outermost beams 42 being supported on rollers 46 rotatably mounted on the side members 36, 38 of the frame 26, the latter being formed also with a centre sill 28, 30, 35 and cross-beams 32, 34 between the sill and side members. In this embodiment the vehicle is provided with two identical single acting shock absorbers 54, 56, each having an enlarged end 62 secured in a structure 70, 72, 74 76 welded and bolted at 78 to the sill plate 35 and also abutting I-beams 88 welded to the plate 35. The shock absorbers also each have an enlarged end 68 abutting a transverse I-beam 30 on the platform, and are supported intermediate their ends by plates 82, 84 bolted together at 86, the plates 84 being welded to the sill plate 35. Referring to Fig. 4, the shock absorber 54 or 56 comprises an outer tubular member 60 secured to the end 62 into which is slidable an inner tubular member 66 secured to the end 68. Secured to the inner end of the member 66 by means of a screw 108, is an annular member 106 which engages the bore of the member 60 and retains a disc 104 provided with a central metering orifice 102. The latter co-operates with a metering pin 92 secured to the end 62, in turn secured to the structure member 72 by a screw 81. The pin 92 has two different tapered portions 145, 146. The member 106 in the fully extended position of the member 66 abuts a spacer ring 110 secured in the bore of the member 60 by having a flange 112 engaging in a recess 114 in the bore and abutted by bearing members 116, 128 which are retained by a member 122. The member 106 has a plurality of longitudinal passages 138 all but one of which are provided with non-return ball valves 142 communicating with the space between the ring 110 and the member 66. Slidable within the member 66 is a piston 132 and the variable volume chamber 136 to the right of the piston 132 is filled with air supplied through a filler port 137. The variable volume chambers 121, 130 on the opposite sides of the variable area orifice 102 are filled with liquid supplied through a filler port 134. In operation, the member 66 is moved inwardly of the member 60 and liquid in the chamber 121 is forced into the chamber 130 to move the piston 132 and compress the air in the chamber 136. Liquid also passes freely through the passages 138 past the valves 142 into the space 140. When the shock absorber has dissipated the kinetic energy of the moving load, the compressed air stored in the chamber 136 moves the piston 132 to the left to force liquid from the chamber 130 to the chamber 121 and so move the member 66 outwardly. However, only one passage 138 in the member 106 permits the flow of liquid from the space between the member 106 and the member 116, the remaining passages 138 being closed by the valves 142 and thus the outward movement of the member 66 is snubbed. Instead of the two single acting shock absorbers 54, 56, a single double acting shock absorber as shown in Fig. 5 may be used. This comprises a casing 150 secured to the centre sill plate 35 and in which is slidable a piston 152 connected to opposed piston-rods 170, 172 each secured to the beams 90 of the platform 22. In this embodiment, the piston 152 is returned to a central position by springs acting between each platform beam 90 and brackets secured to the sill plate 35, as described with reference to Fig. 12 (not shown). The walls of the chambers 184, 182 on each side of the piston 152 are provided with tapered grooves 186 of semicircular crosssection the area of the orifice formed between the piston and one groove thus varying as the piston moves in either direction from the central position. In modifications, the grooves are rectangular in cross-section or are replaced by two tapered lands which co-operate with a rectangular slot in the piston periphery, all as described with reference to Figs. 7 and 9 (not shown).